THE BIOASSAY OF GROWTH HORMONE IN SNELL'S DWARF MICE: EFFECTS OF THYROXINE AND PROLACTIN ON THE DOSE—RESPONSE CURVE

Abstract

SUMMARY Pituitary growth hormone has a dose-dependent growth promoting effect in pituitary dwarf mice (Snell's strain), and this effect can be used as the basis of a bioassay for the hormone. Prolactin and thyroxine also promote growth in these animals, and the effects of these hormones in combination with growth hormone were studied, in order to see whether their presence might enhance the precision or sensitivity of the growth hormone assay. When prolactin and/or thyroxine were administered with growth hormone, the growth response observed was no greater than the sum of the effects of the hormones given separately; in some cases it was less. Neither prolactin nor thyroxine increase the sensitivity or precision of the growth hormone bioassay. The implications of these results for theories about the mechanisms of growth promotion by these hormones are considered.